Compensating radial work support for an internal centerless grinder



June 17, 1958 R. CANN ET AL 2,838,888 COMPENSATING RADIAL WORK SUPPORT FOR AN INTERNAL CENTERLESS GRINDER Filed July 17, 1957 v mvENTofis Roald Larzn W Jbhn L0lly' j g "kw WWW ATTORNEYS COMPENSATENG RADIAL WORK SUPPORT FOR AN INTERNAL CENTERLESS GRINDER Roald Cann, Weathersfield Township, Windsor County, and John W. Lovely, Springfield, Vt., assignors to Bryant Chucking Grinder Company Application July 17, 1957, Serial No. 672,424 4 Claims. (Cl. 51103) This invention relates to improvements in internal nited States Patent 2 centerless grinding machines of the type wherein an annular workpiece is radially supported on a preformed outside periphery for rotation in frictional relationship to supporting shoes peripherally spaced along the surface and a tool is applied to its inner periphery to generate an internal surface concentric with the preformed outer surface. Anexample of this type of grinding machine is disclosed in the U. S. patent to Arms et al. 2,635,395. More particularly, this invention relates to a compensating radial work support for an internal centerless grinding machine such as described above.

In internal centerless grinding, typical annular workpieces, such as raceway rings for antifriction bearings, must be produced at a fast rate while holding narrow tolerance limits in concentricity and diametrical dimensions. Because of prevailing economic and technological reasons, the preformed outside surfaces are allowed to have dimensional variations between successive workpieces and the internal grinding machine is expected to.

accept such workpieces at random and constantly therein produce a hole of predetermined diameter concentric with the preformed radially-supported outside perimeter. A1-

though this condition of added complication could be wholly, or at least partially, remedied by pregaging and classification grouping of workpieces, any such means have heretofore proven uneconomical. From the foregoing it follows that in order to accomplish the above stated desirable result the centers of successive workpieces, at least in the final phase of the grinding process, always must be located at a predefined position irrespective of diametrical variations occurring at random between consecutive workpieces. Hence, when the feed movement is constant from a line through the centers of the respective workpieces and normal thereto, the inside diameter of the hole generated will be constant.

It is therefore an object of this invention to provide means for randomly accepting successive workpieces with different outside diameter and supporting these workpieces for internal centerless grinding with the centers of the workpieces in predetermined positions.

Another object of this invention is to provide a radial work support that automatically compensates for random difierences in outside diameters between successive workpieces.

A further object of this invention is to provide a device wherein the radial support means are arranged in a manner so that at least during the final part of the grinding operation, the center of the workpiece is located at a controlled predetermined position relative to the contact point between the workpiece and tool.

In general, the above objects are accomplished by a fixed support which positions the centers of different diameter workpieces on a single line normal to the line of feed, in combination with means to displace the workpiece from this support during the rough grinding operation and support the workpiece against a radial support 2,838,888 Patented June 17, 1958 adjacent the line of feed for the purpose of supporting the wall of the workpiece adjacent the point where the grinding force is applied. After the rough grinding has been completed in this position, the workpiece is allowed to rest on the first-mentioned fixed support which ac-' curately defines the position of the normal line through the centers of successive workpieces at a predetermined distance from the leading edge of the tool so that when the tool is moved a predetermined feed distance the holes generated in successive workpieces having random outside diameters will be of a constant diameter.

In other words, during the phase of the grinding process when the greatestforces acting on the workpiece are present, the workpiece is restrained to be radially sup; ported in a grinding throat formed by one pair of shoes straddling the resultant of said forces with one shoe in proximity of the line of feed; and during the final phase of the grinding process when substantially lesser forces are acting onthe workpiece, and with the aforesaid re straint removed, the workpiece, by virtue of the kinetics of the system, is compelled to be radially supported me grinding trough formed by another pair of shoes angularly spaced about a line normal to the line of feed.

For a more complete understanding of the invention,

' reference may be had to the following description taken in-connection with the accompanying drawings wherein:

Figure 1 is a side elevation with a portion in section, illustrating a preferred embodiment of the compensating radial work-holder of the present invention.

Figure 2 is similar to Figure 1 with the operative elements in a different position for the rough grinding operation.

Referring to Figure 1, a'surface 10 of a grinding machine bed portion supports a headstock which contains a rotatable work driver having a face normal to its rotational axis, and this work driving face portion axially supports and drives an annular workpiece W, as described in Patent 2,635,395 referred to above. A rotatable spindle 14 carries a tool T which is positioned within the annular workpiece. The headstock-supported workpiece and the tool-carrying spindle are arranged for a relto the face of. bracket 16 and having supporting shoes 24 and 26 fixedly nested therein. These shoes, which are angularly spaced from intersecting line N normal to line F, have face portions and 2'7, which form radial supports for the outside periphery of workpiece W.

A movable radial support consists of a member 30 which is hingedly attached at 28 to the fixed support 20. This hinge may be a weakened portion of the support or may be flexible reeds or other suitable-type hinges which allow pivotal movement about the hinge axis only. A support shoe 32 is carried by and movable with the member 30 and this shoe has a face portion 33 for contacting and supporting the periphery of the workpiece. The hinge portion 28 is arranged to normally bias the shoe 32 away from the periphery of the workpiece W to a position outside a circle defined by the outside diameter of the smallest permissible diameter workpiece when it is supported on shoes 24 and 26. (Fig. 1).

A further fixed radial support for the workpiece W is provided by a shoe 36 having a face portion 37. This shoe is nested in a fixed bracket 34 which is attached to the bracket 16 by means of cap screws 35. This support is located in proximity of the line of feed F where cylinder 40 having a piston 42 therein. A fluid conduit 44 is provided for admitting fluid pressure to the working end of the piston. The piston carries an extension or piston rod 43 having an adjustable stop 46 threaded at the end thereof. This step contacts a surface of support member 30 for moving this support. The lower end 48 of cylinder 40 functions as a positive stop limiting the outward movement of the movable support shoe 32, and the other end 49 of the cylinder 4 is the positive stop limiting the displaced position of the shoe 32.

The operation of the device is as follows: The machine is initially positioned to place the faces 25 and 27 of the two-point support in a definite position to locate the center 0 of a median outside diameter workpiece on the line P where the center of the spindle 14 is also located. The movable shoe may then be adjusted by placing a minimum permissible diameter workpiece on the faces 25 and 27 of the two-point support. With the maximum permissible diameter workpiece seated on the two-point support, the single point radial shoe may be adjusted to place face 37 in its proper position as described above. It is noted that for the sake of clarity the clearances shown between the workpieces and shoes are grossly exaggerated as in reality they are only a few thousandths of an inch. After these adjustments, fluid pressure is introduced to the working end of piston 42, placing face 33 of shoe 32 in the position as shown in Fig. 2. When a workpiece is placed on the support with an end face against the work-driving spindle, the workpiece will be compelled to rotate and will be seated against face 37 and face 33 in the same manner as described in the patent referred to above; namely, 2,635,395. The infeed of the tool along line F in the direction of the arrow is started normally at a high rate, and a predetermined amount of stock is removed in this first phase of the grinding operation. After a predetermined amount of stock has been removed, the feed is slowed down, the fluid pressure acting on piston 42 is relieved, and the spring bias forces the face 33 back to the original position as shown in Fig. 1. The force from the tool during this lower feed rate is less than the force of the driver acting on the workpiece as described in above referred to Patent No. 2,635,395. As a result the workpiece now seeks a seating position against faces 25 and 27 and, because of the angular spacing of these shoes, the center of the workpiece will always be located on the line N positioned at a predetermined positive distance TF from the leading edge of the tool T. By executing the final phase of the grinding operation with workpiece seated only against faces 25 and 27, it will be evident that a fixed amount of infeed will consistently generate a hole of predetermined diameter and concentric with the outside periphery of the workpieces irrespective of differences'between the outside diameters of successive workpieces.

Applicants have disclosed a preferred embodiment of an improved radial workpiece support for an internal centerless grinder for the purposes of illustration only, and the disclosed embodiment is not considered limiting, as the invention is limited only by the scope of the appended claims, wherein applicant is entitled to a full range of equivalence.

We claim:

1. In an internal grinding machine having a rotatable workdriver, a tool adapted to be placed in working relationship to the interior of an annular workpiece on which an internal surface is to be generated, means to impart a relative transverse movement to the tool and workdriver between the axes thereof along a line of feed extending through the axis of the tool; a compensating V radial work-support apparatus comprising: a first pair of fixed shoes, angularly spaced about a line normal to the line of feed, work contacting face portions of these shoes spaced at a periphery of a circle defined by the work contacting faces of the shoes and having its center at the intersection between the line normal and the line of feed;

a second pair of shoes, the first of these fixedly located with a work supporting face portion thereof radially outside said circle and in proximity of the line of feed, where a wall of a workpiece may be interposed between this shoe and the tool, and the second of these shoes movable between an inoperative and an operative position, where its work supporting face, in the inoperative position will'be positioned outside said circle, and in the operative position will be positioned inside the circle, and together with the first shoe forms a grinding throat removed from the work supporting trough defined by said first pair of shoes; and means to move said second shoe.

2. An apparatus as defined in claim 1 where said first shoe of the second pair of shoes in the operative position of the movable shoe unyieldingly resists forces acting thereon through the intermediary of said wall.

3. A device as defined in claim 1, wherein said supportrnoving means comprises:- means biasing the movable support to a normal position, and a fluid motor for moving this support to its supporting position.

4. A device as defined in claim 3, wherein said supportmoving means includes positive stops limiting the movement of the movable support to define the normal and displaced position thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,478,607 Theler et al. Aug. 9, 1949 2,646,652 Blood July 28, 1953 2,680,939 Humes June 15, 1954 2,758,427 Quimby Aug. 14, 1956 2,793,479 Arms et al. May 28, 1957 

